When a group of people (usually women) get together and bash other women. Usually begins when one person makes a simple negative comment about a female who isn't present. This quickly escalates into a full out bash against the female, and will most likely lead to the bashing of more women.

Female 1: Haha, you remember when Becky blocked me on Facebook?
Female 2: Yea, what a whore.
Female 3: I heard she's a complete slut, too. She hangs out with Sarah. I hate them both.
Male 1: You've only been here 10 minutes, and you've already started a Bitch Bash.